Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752996AbaFFB4K (ORCPT ); Thu, 5 Jun 2014 21:56:10 -0400 Received: from mga01.intel.com ([192.55.52.88]:25891 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752663AbaFFB4I (ORCPT ); Thu, 5 Jun 2014 21:56:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.98,985,1392192000"; d="scan'208";a="550544877" Date: Fri, 6 Jun 2014 09:55:24 +0800 From: Liu ShuoX To: linux-kernel@vger.kernel.org Cc: "H. Peter Anvin" , Ingo Molnar , Peter Zijlstra , Zhang Yanmin , yanmin_zhang@linux.intel.com Subject: [PATCH v3] perf: fix kernel panic when parsing user space CS saved in pt_regs Message-ID: <20140606015524.GA19246@lskakaxi-intel> References: <20140605023610.GA12905@lskakaxi-intel> <20140605071919.GD3213@twins.programming.kicks-ass.net> <20140605073321.GA14869@lskakaxi-intel> <20140605074008.GB14869@lskakaxi-intel> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20140605074008.GB14869@lskakaxi-intel> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zhang Yanmin ChangeLog V3: Keep rsp pointing to pt_regs before sysexit. ChangeLog V2: Before sysexit, perf NMI might arrive. There is still a race. Here we change rsp to keep it pointing to pt_regs->orig_ax. In addition, after sti, before sysexit, an irq might arrives. That causes more chances for perf NMI to jump in. We hit a kernel panic when running perf to collect some performance data. kenel is x86_64 and user space apps are 32bit. BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 IP: [] get_segment_base+0x71/0xc0 PGD 6c65f067 PUD 0 Oops: 0000 [#1] PREEMPT SMP Modules linked in: <...> CPU: 1 PID: 304 Comm: Binder_2 Tainted: G W O 3.10.20-263902-g184bfbc-dirty #14 task: ffff8800764dc300 ti: ffff88006c6e8000 task.ti: ffff88006c6e8000 RIP: 0010:[] [] get_segment_base+0x71/0xc0 RSP: 0018:ffff^X8007ea87b98 EFLAGS: 00010092 RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000009 RBP: ffff88007ea87ba8 R08: ffffffff83143b3c R09: ffffffff831848a8 R10: 0000000000000000 R11: 00000000001bf2d8 R12: 0000000000000000 R13: ffff88006c6e9fd8 R14: ffff88006c6e9f58 R15: ffff8800764dc300 FS: 0000000000000000(0000) GS:ffff88007ea80000(006b) knlGS:00000000f704add0 CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 CR2: 0000000000000004 CR3: 0000000076588000 CR4: 00000^P00001007e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Stack: ffff88005f266c00 0000000000000000 ffff88007ea87c18 ffffffff82013cac ffff88007ea87d58 00000016fe4704a0 00000000000001a7 ffff88007ea87ef8 ffff88005f266c00 ffff88007ea87ef8 ffff8800!e07b400 ffff88005f266c00 Call Trace: [] perf_callchain_user+0x15c/0x240 [] perf_callchain+0x134/0x180 [] ? local_clock+0x47/0x60 [] perf_prepare_sample+0x1bb/0x240 [] __perf_event_overflow+0x147/0x230 [] ? x86_perf_event_set_period+0xd8/0x150 [] perf_event_overflow+0x14/0x20 [] intel_pmu_handle_irq+0x1c2/0x270 [] ? call_softirq+0x30/0x30 [] perf_event_nmi_handler+0x21/0x30 [] nmi_handle.isr!.1+0x59/0x=0 [] default_do_nmi+0x58/0x240 [] do_nmi+0xb8/0xf0 [|ffffffgf828aebe7>] end_repeat_nmi+0x1e/0x2e [] ? call_softirq+0x30/0x30 [] ? call_softirq+0x30/0x30 [] ? call_softirq+0x30/0x30 Basically, ia32 uses sysenter to start system calls. sysexit_from_sys_call=>trace_hardirqs_on_thunk. Before calling, sysexit_from_sys_call already pops up pt_regs, then trace_hardirqs_on_thunk would reuse pt_regs space. If perf NMI happens here, perf might use a bad pt_regs. The patch fixes it by keeping rsp pointing to pt_regs. Signed-off-by: Zhang Yanmin Signed-off-by: Liu Shuox --- arch/x86/ia32/ia32entry.S | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 4299eb0..d2f905b 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -172,15 +172,16 @@ sysexit_from_sys_call: andl $~0x200,EFLAGS-R11(%rsp) movl RIP-R11(%rsp),%edx /* User %eip */ CFI_REGISTER rip,rdx - RESTORE_ARGS 0,24,0,0,0,0 - xorq %r8,%r8 + RESTORE_ARGS 0,-ARG_SKIP,0,0,0,0 + movq EFLAGS-R11(%rsp),%r8 /* rflags */ + movq RSP-R11(%rsp),%rcx /* User %esp */ xorq %r9,%r9 xorq %r10,%r10 xorq %r11,%r11 - popfq_cfi + pushq_cfi %r8 /*CFI_RESTORE rflags*/ - popq_cfi %rcx /* User %esp */ - CFI_REGISTER rsp,rcx + popfq_cfi + xorq %r8,%r8 TRACE_IRQS_ON ENABLE_INTERRUPTS_SYSEXIT32 -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/